A voltage regulator includes a linear mode regulator having a high pass filter
circuit connected between its output and an output node, and a switch mode regulator
having an low pass filter circuit connected between its output and the same output
node. The high pass filter passes high frequency AC current provided by the linear
mode regulator to the output node and reduces the low frequency AC and DC currents
to substantially zero, and the low pass filter prevents the high frequency AC current
produced by the linear mode regulator from being drawn by the switch mode regulator
and passes the low AC and DC currents provided by the switch mode regulator to
the output node. Thus, the present regulator offers the high response speed and
low noise of a linear mode regulator, and the high power efficiency and large continuous
output current capability of a switch mode regulator.